348 grounds

I have searched the threads and very possibly missed the information I am looking for. Question: where are the locations of the grounds on a 1992 348 TS. I keep seeing instruments come and go and the only logical explaination is a bad ground. Where do I start to look and what do I have to do to get to the areas??
Thank you,
jeff

 

What specific instruments are you losing Jeff ?

 

I lose the speedometer/odometer and then a bump in the road will return it to operation, also the fuel gauge will do the same. Not necessarily at the same time.

jeff

 

The speedo/odo is due to failing wiring in the speedo sensor 99% of the time. The wiring fails where it exits the sensor. The fuel guage is a separate issue-I don't know about that one.

 

I had a simular issue several years back. My 348 would always have the check engine 1-4 light. It turned out to be the battery ground. The battery ground that you can disconnect to charge the battery may look clean. However, I learned to emory cloth those ends, put them back together and not to disconnect it unless absolutly necessary. I also use tie wraps to make sure the ground is tight.

Try that, you may find it works. I have not had any issues since then.

Dan

 

Check the connector to the back of the speedo, and the connector to the speedo sender. Clean them up good. It is possible the sender is on the way out too...they fail with great regularity.

 

Okay there are two basic grounds.

1) The ground from the transmission to the frame.

2) From the negative post on the battery to the frame.

Then you also have the grounds going to the top of the cam covers, and the ground up under the intake plenum.

 

All good stuff for me to check and Thank you everyone, one final question, I have been told there is a ground connection behind the driver side a/c vent on the left side of the dash. Is this the case and just for grins, how do I get the ducts out, they are tacky and need a good cleaning too.

Thanks,

jeff

 

There are grounds everywhere in these dumb cars. There is one behind dash on left and right but I am not sure you can get to them with dash in place. Also there is a bunch behind the passerger footwell fuesbox. These dumbys have the Fuel pump grounds from way back in the fuel pump run all the way to the behind fusebox ground terminal! It is no wonder these car weight 5 milion lbs and run so badly. I was lucky to have this wiring harness fire in my 348 racecar. It caused me to strip out all the unneded wiring foward of the shifter. The car ran awesome and more reliable than ever with amazing crisp starts. I was so pleased. last weekend I stripped out all the unneeded wires aft fo the shifter, repositioned grounds, 86ed the huge power cables from rear to front, stripped out alll the tail light wiring except the stop lamps and wow! My car starts and runs even better. I did not know it was possible. Now a push of the start button and the car jumps to life on barely the first pulse. Amazing how bad the pem wiring is. I am truely down to ABS electronics and ECU electronics and two tail lights what a difference it makes.

 

Have you weighed all the wiring?

 

Not really but Bruce would be jealous! It is in the 20+ pound range. It is all the wiring, gromets, tape, connectors, ground terminals, harness holders etc... It is amazingly heavy.